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Monday, 24 September 2012

Dynamic and Static Cache in Informatica

In
Informatica Lookup transformation we have the option to the cache the Lookup
table(Cached Lookup).If we don’t use the lookup cache its is called as Uncached
Lookup.

In Uncached lookup we do lookup on the
base table and will return output values based on the Lookup condition. If the
lookup condition is matching it returns the value from Lookup table or cache
.And if lookup condition is not satisfied then it returns either NULL or
default value. This is how Uncached Lookup works

Now we
will see what a Cached Lookup is!

In Cached lookup the Integration Service
creates a Cache whenever the first row in the Lookup is processed. Once a Cache
is created the Integration Service always queries the Cache instead of the
Lookup Table. This saves a lot of time.

Lookup
Cache can be of different types like Dynamic Cache and Static Cache

What is a Static Cache?

Integration
service creates Static Cache by default while creating lookup cache. In Static
Cache the Integration Service does not update the cache while it processes the
transformation. This is why it’s called as Static.

Static
Cache is same as a Cached Lookup in which once a Cache is created the
Integration Service always queries the Cache instead of the Lookup Table.

In Static
Cache when the Lookup condition is true it return value from lookup table else
returns Null or Default value.

In Static
Cache the important thing is that you cannot insert or update the cache.

What is a Dynamic Cache?

In Dynamic
Cache we can insert or update rows in the cache when we pass the rows. The
Integration Service dynamically inserts or updates data in the lookup cache and
passes the data to the target. The dynamic cache is synchronized with the
target.